BitTorrent serverless chat replaces usernames with crypto keys

"With BitTorrent Chat, your identity is a cryptographic key pair."

BitTorrent, Inc. is developing a serverless instant messaging system that relies on public key encryption to protect the privacy of communications, identifying users not with traditional usernames but with cryptographic key pairs.

The company, which develops the BitTorrent peer-to-peer protocol as well as the BitTorrent and μTorrent file sharing software, announced the forthcoming chat software in September and revealed some details on how it will work in a blog post today. It reads:

With BitTorrent Chat, there aren’t any “usernames” per se. You don’t login in the classic sense. Instead, your identity is a cryptographic key pair. To everyone on the BitTorrent Chat network at large, you ARE your public key. This means that, if you want, you can use Chat without telling anyone who you are. Two users only need to exchange each other’s public keys to be able to chat.

Using public key encryption provides us with a number of benefits. The most obvious is the ability to encrypt messages to your sender using your private key and their public key. But in public key encryption, if someone gains access to your private key, all of your past (and future) messages could be decrypted and read. In Chat, we are implementing forward secrecy. Every time you begin a conversation with one of your contacts, a temporary encryption key will be generated. Using each of your keypairs, this key will be generated for this one conversation and that conversation only, and then deleted forever.

Underlying this system is a Distributed Hash Table (DHT) which finds IP addresses, removing the need for a central server to route messages, the company explained.

"If you understand the fundamentals of the DHT, you might be wondering, 'How is a DHT more secure? Aren’t you giving your IP address out to the entire DHT? That’s LESS secure than a central server!'" BitTorrent wrote. "With Chat, we are expanding on what we can use the DHT for. We have updated our DHT protocol to support encryption. The new DHT protocol enables users to find each other securely and privately."

You can sign up for the BitTorrent Chat private alpha, but don't expect to be granted access right away. BitTorrent spokesperson Christian Averill told Ars that the system is only being used internally as of now.

Averill noted that the key pair scenario described above is just one of the ways BitTorrent Chat will secure communications—users will have other options. "There will be other, simpler ways that we also support for people who are less technical," Averill said. "Those details will follow at a later date."

BitTorrent, Inc. isn't saying when Chat will be available, but Averill said it will likely follow a similar development pattern as BitTorrent Sync, a Dropbox-like file syncing system that relies on P2P technology. That would mean a private alpha testing stage would be followed by a public alpha few months later and a beta release a few months after that.

Interest in more secure file syncing and chat technologies has increased in the months following leaks detailing how the National Security Agency spies on personal communications. Users who don't want to wait for BitTorrent Chat can encrypt instant messages today using Off-the-Record, which can be used through plugins for chat clients.